Known pressure containers are usually formed by a metal pressure vessel in which a utility agent, e.g. hair lacquer, perfume, liquid soap, mustard etc., is placed. To force the utility agent out of the pressure container producers usually use freon, but at present also less harmful agents such as propane-butane are used. It is also known to use air in containers, usually provided with a special arrangement of the inner space of the pressure vessel for not allowing the agent to contact the air.
Another known solution is a use of memory characteristics of elastic material, e.g. of a rubber, to force out the utility agent.
Yet another known solution is a pressure container comprising a protective flask in which an elastic bag is arranged, the elastic bag being sealed to a charge and discharge valve situated in the lid of the protective flask. In this known solution, in order to prevent a contact between the utility agent and the inner surface of the elastic bag, a foil which is inert to the utility agent and which is fixed also to the valve is used. The utility agent is forced out of the pressure container by the contraction of the elastic bag.
There is no gaseous working medium used in the above mentioned case. Its practical use is nevertheless problematic because a relatively large content remains in the elastic bag and cannot be forced out by said bag.
Another pressure container comprising also just a protective flask, e.g. of a plastic material, is provided with a closed hollow elastic storage bag sealed by the lid periphery, and with a charge valve which serves at the same time as a discharge valve arranged over the elastic storage bag and in the lid. The discharging of the utility agent out of the space above the upper part of the closed concave elastic storage bag is performed in this case by contraction of the material of the concave upper part of the closed hollow storage bag. Then in the last phase it is performed by expansion of the gaseous medium compressed during filling of the pressure container inside of the closed hollow elastic storage bag which results in complete discharge of the utility agent.
Hand-operated fire-extinguishers, beside other fire-extinguishing means, are also known and used. These hand-operated fire-extinguishers comprise usually steel pressure container with a fire-extinguishing agent, e.g. with water, powder, foam, etc., which is either under constant pressure of gas, or which is provided with a closed, easily breakable ampule with a chemical creating over-pressure when mixed with water or other chemical, the overpressure being able to discharge the fire-extinguishing agent out from the fire-extinguisher.
The use of pressure container with freon serving as the working medium is on the decline, due to the well known reasons. When using other working media it is necessary to take various steps to prevent any contact between the working medium and the utility agent, and this leads to an increase of operating costs. Besides that, the propane-butane, which is used in such devices, is an inflammable gas. This property excludes the possibility of using said gas e.g. in fire-extinguishers. That goes for air as well, as the contact between the air and the utility agent is usually undesirable and if used in a fire-extinguisher it would support the fire.
It is not advantageous to use chemicals to create an overpressure in fire-extinguishers. A disadvantage of some of the fire-extinguishers is namely the possibility of their explosion.